1. Field of the Invention
This invention relates to a bi-directional valve constructed and arranged for non-surgical insertion within the fundus of an esophagus in the vicinity of its lower gastroesophageal sphincter for permanent installation therein without requiring surgery to open the esophagus to attach said bi-directional valve thereto, thereby avoiding the need for antacid medicines or other surgery.
2. Introduction of the Problem of GR Disease
Gastroesophageal Reflux Disease (or Reflux Esophagitis) is a disease which results from an improperly functioning lower gastroesophageal sphincter. The lower gastroesophageal sphincter operates on a pressure differential basis; when the pressure on the esophageal side of the sphincter exceeds a certain critical value, the sphincter opens and material passes from the esophagus into the stomach. When the pressure on the gastric side of the sphincter exceeds a different critical pressure, the sphincter opens and material passes out of the stomach and into the esophagus. The pressure at which the sphincter opens varies from person to person and is difficult to measure, but manometric studies reveal that the valve opens due to pressure as little as 5 mm Hg on the esophageal side. However, a healthy valve does not open unless pressures of more than 80 mm Hg exist on the gastric side. In patients suffering from gastroesophageal reflux disease, the pressure at which the valve distends is lowered, the threshold at which reflux occurs also is not definite. However, reflux becomes likely in people with esophagitis, if lower esophagus sphincter pressure is below 7 mm Hg. Once reflux begins, inflammation of the esophagus may set in, which, in turn, weakens the sphincter. This causes a vicious cycle of reflux causing sphincter hypertension, which increases the likelihood of reflux. The sphincter gradually degenerates. The most common symptom of gastroesophageal reflux is dyspepsia, which affects around 7% of people daily, and 30-50% of people intermittently.
Dyspepsia is defined as an uncomfortable burning sensation located below the sternum, tending to move up to the neck. Dyspepsia may mimic the symptoms of a myocardial infarction or severe angina pectoris. Other symptoms of esophageal reflux include regurgitation, dysphagia, odynphagia, hemorrhage, water brash, pulmonary manifestations due to acid aspiration (including bronchitis and bronchospasms). Repairing esophageal reflux usually requires corrective surgery. Esophageal ulcers are also serious manifestations of gastroesophageal reflux disease because they are manifested by intense continuous pain and can present acute, life threatening hematemesis due to erosion into a blood vessel. Barrett's Epithelium is the replacement of normal squamous epithelium in the esophagus by columnar epithelium. Barrett's Epithelium is also serious because it can be a premalignant condition. The incidence of adenocarcinoma was found to be 10 percent.
Another important complication of esophageal reflux is stricture. Once the esophagus lining is damaged, the cells receive impulses to produce fibrous tissues and adhesion. This is the mechanism by which the esophagus heals itself. The most common clinical manifestation of stricture is dysphagia. Unlike dysphagia from non-strictured esophageal reflux, dysphagia caused by a stricture is a progressive disorder in that the size of the bolus that can pass into the stomach progressively becomes smaller. Dysphagia weakens the peristalsis of the esophagus which, in turn, makes it harder to open the valve by reducing the esophageal pressure. If a piece of food can not pass through the stricture, regurgitation will result. Stricture is a disorder particularly relevant to this invention.
A common cause of esophageal reflux is hiatal hernia. One report showed that 21% of upper gastrointestinal disorders are due to hiatal hernias. Because some patients with hiatal hernia require surgery, there is an immediate need for patients with this condition to utilize this invention.
3. Present State of the Art
A. Non-invasive State of the Art
There are a variety of different techniques designed for treatment of less serious cases of esophagitis. Changing the nocturnal posture of patients is sometimes a first step, although it has limited effectiveness. Antacids can be prescribed to modify the fluid reflux so as to reduce the pain of dyspepsia. Some antacids cause diarrhea, others cause constipation. Other prescribed treatments include calcium carbonate, Cimetidine, or other H2 blockers. The effectiveness of these treatments vary. None totally eliminate dyspepsia. They have to be taken constantly at great cost and any cessation of them causes the pain to return without modification. They may also cause liver damage or interact with other medications.
The major problem with non-invasive techniques is that they do not eliminate reflux. They may temporarily change the nature of reflux to make it less acidic, or alter the occasions of its occurrence making it easier to sleep, but reflux will still occur. They are also temporary techniques and the patients must constantly take drugs for the rest of their lives.
B. Patents Relating to this Invention
U.S. Pat. No. 3,159,176 to Russell et al, issued Dec. 1, 1964, discloses a bi-directional valve of the duck-bill type in which reverse flow is accomplished outside the body of the valve by having reverse flow pressures in excess of a predetermined value lift a flexible umbrella portion off its seat. The construction of the Russell et al valve is such that it would require modification of the emerged umbrella to avoid its dislodgement and its tendency to cause choking.
The valve in the Russell et al patent is designed for hydrostatic pressure. Esophageal pressure is dynamic. Peristalsis of the esophagus induces the valve opening pressure. The Russell valve has a long cylindrical opening which is designed to allow fluid to accumulate. This does not work with bolus, which is solid. When bolus accumulates, it begins to smell, and deprives a person of nutrition.
U.S. Pat. No. 3,657,744 to Ersek, issued Apr. 25, 1972, shows a tool that invades the wall of a blood vessel in order to expand a housing of expanded metal that supports a prosthetic member such as a heart valve. Expansion of the housing containing the prosthetic member imbeds the expanded metal housing into the walls of the blood vessel(s) within which the housing is inserted for permanent installation.
U.S. Pat. No. 3,875,928 to Angelchik, issued Apr. 8, 1975, shows a prosthesis in the form of a generally C-shaped cushion member that is large enough to prevent extension of the gastric fundus into the thoracic cavity through an enlarged esophageal hiatus. The prosthesis is wrapped around the distal end of the esophagus to prevent the stomach from sliding into the chest area through the enlarged hiatal hernia. While this patent prevents the extension of a hernia, it does not necessarily stop reflux. Furthermore, closing the opening between the esophagus and the stomach can cause the same symptoms as stricture, mainly obstruction of food which leads to dysphagia. Also, closing the stricture may also make it impossible to regurgitate, which is a dangerous situation. Other problems that may arise from the Angelchik technique include gastric ulcers, fistula formation and general surgical complications. One surgical complication is "gas bloat" syndrome which is caused by gas not being able to leave the stomach. This was reported in 15% of patients in one study. It has been reported that 20% of patients who have primary antireflux surgery require reoperation due to recurrent reflux.
U.S. Pat. No. 4,181,145 to Mitchell, issued Jan. 1, 1980, shows a two-way check valve having a valve body with an opening covered by a flexible wall in such a manner that it defines two slits. The walls of the opening are sloped in such a manner that a forward flow pressure across the opening causes forward flow through one of the slits while the second slit remains closed. Pressure in the opposite direction causes flow through the second slit in said opposite direction while the first slit remains closed. The valve of this patent is used in a disc brake assembly and does not appear to be adaptable for use within an esophageal cavity.
The Mitchell valve is designed for pneunatic pressure. It is incompatible for food bolus (a mixture of liquid and solid). The Mitchell valve contains a large surface area on which food build-up can take place. The valves 52 and 54 are set at an angle which would allow food build-up, and once the valve opens, it would jam. The membrane 68 between the two valves 52 and 54 is so thin and pliable that it would distend and/or be dissolved by the gastric acid. The Mitchell notches 76 and 80 reduce the pressure differential required to open the valves to levels difficult to control. Also, the Mitchell construction is too wide to work in the esophagus and thus, it would bend and become dislodged.
U.S. Pat. No. 4,067,414 to Funke, issued Jan. 10, 1978, shows a one-way check valve of the duckbill type located at the outlet end of a molded plastic fitting to have lubricant pressure cause the check valve to open and feed lubricant into a housing and also force the fitting radially outwardly to engage a roughened inner wall of the housing. The Funke fitting would not work in the esophagus because it is designed to accommodate hydrostatic pressure. Any solid piece of food would get stuck in the valve. Its gastric end is too thin; anyway, the area inside the valve is too small to accommodate bolus. And of course it is unidirectional. The enlarged flange would make it impossible to use the check valve within an esophagus.
U.S. Pat. No. 4,434,810 to Atkinson, issued Mar. 6, 1984, shows different embodiments of bi-directional pressure relief valves that operate to permit forward and reverse flow at different forward and reverse flow pressures. The outer diameter of the valves are slightly greater than the inner diameter of the opening within which the valve is received. Since it is necessary to slide a valve along the length of the esophagus before it reaches a desired operating position for performing the objects of this invention, the Atkinson valve would be difficult to install. The Atkinson valve is entirely incompatible for insertion into the esophagus. Its shape would cause food to collect on the flange 16 and inside the housing. This valve would induce dysphagia. Furthermore, the construction of the Atkinson valve is much more complicated than is desirable.
U.S. Pat. No. 4,436,519 to O'Neill, issued Mar. 13, 1984, shows a one-way flow valve for use with hemostasis apparatus and emphasizes a fast connect and disconnect means and an elongated rib perpendicularly oriented with respect to a slit. The apparatus is unsuitable for use as a bi-directional valve. The O'Neill valve is incompatible for the same reason as the Atkinson valve. Its shape would cause dysphagia.
U.S. Pat. No. 4,524,805 to Hoffman, issued June 25, 1985, discloses a one-way duckbill valve, which would be unsuitable, if inserted in the vicinity of the gastroesophageal junction, as a bi-directional control valve. Furthermore, the Hoffman valve as constructed is likely to allow food to accumulate at the sides of the housing leading to the possibility of dysphagia. Also, if food bolus gets stuck in the valve corners, the stuck bolus is likely to prevent the valve from operating as desired to prevent reflux. The Hoffman valve is stressed to provide some portions that are structurally weaker than other portions. The structurally weak portion can cause the Hoffman valve to distend, which could increase the critical esophageal pressure at which the valve operates, could disrupt operation of the valve and eventually lead to dysphagia. The Hoffman valve is completely flexible and can be crushed by contraction of the esophagus during peristalsis. The crushed valve structure can be passed into the stomach, can be regurgitated, and then would be susceptible of causing either dysphagia or choking. The Hoffman valve has a structure that ensures unchanging opening pressure. This esophageal pressure required to open the Hoffman valve cannot be determined for any individual patient until after the valve is inserted, and cannot be modified while the valve remains inserted without performing invasive surgery on the esophagus. The Hoffman valve has a rigid flange formed with sharp corners that can irritate the epithelial lining of the esophagus or lacerate the esophagus and cause hemorrhaging.